Hybird vehicle drive control apparatus, hybird vehicle drive control method, and program thereof

ABSTRACT

A hybrid control device including a drive motor that compensates for an excessive or a deficient amount of engine torque with respect to a vehicle requirement torque and a controller that detects a torque limit index, which is an index that limits a drive motor torque, determines whether the torque limit index has exceeded a threshold value, limits the drive motor torque when the torque limit index has exceeded the threshold value, and adjusts the engine torque in accordance with a limiting of the drive motor torque.

BACKGROUND OF THE INVENTION

[0001] 1. Field of Invention

[0002] The invention relates to a hybrid vehicle drive control device, ahybrid vehicle drive control method and a program thereof.

[0003] 2. Description of Related Art

[0004] Conventionally, there exists various types of hybrid vehicles.For example, in a first type of hybrid vehicle, an engine and a drivemotor are directly connected, so that an engine torque and a drive motortorque can be transmitted to a drive wheel. Thus, when torque that isrequired to make a hybrid vehicle run (vehicle requirement torque) issmall, the engine is driven at the most efficient operation point on anoptimal fuel consumption curve. The drive motor torque that correspondsto the amount of the engine torque in excess of the vehicle requirementtorque is also absorbed as regenerative torque, and electrical energy isgenerated by the drive motor, which is used for charging a battery. (SeeJapanese Patent Laid-Open Publication No. 11-82258).

[0005] Furthermore, a second type of hybrid vehicle has a planetary gearunit that is provided with a sun gear, a ring gear and a carrier. Thecarrier and the engine are connected, the ring gear and a drive wheelare connected, and the sun gear and a generator are connected, wherein aportion of the engine torque is transmitted to the generator, and theremaining amount is transmitted along with the drive motor torque to thedrive wheel.

[0006] In this case, in an overdrive state that reduces the enginetorque in the engine and increases a speed of revolution of the engine,(the engine speed) electrical energy is generated by absorbing asregenerative torque the drive motor torque that corresponds to a portionof the engine torque transmitted from the engine to the drive motor, andthe generator is driven as an electric motor using this electricalenergy. (See Japanese Patent Laid-Open Publication No. 10-325344).Further, in one known example of the second type of hybrid vehicle, thehybrid vehicle, when running an engine to generate power by a generator,is moved backward by causing a drive motor to generate drive motortorque in a reverse direction such that it is sufficient to overpowerthe engine output (refer to U.S. Pat. No. 6,005,297).

SUMMARY OF THE INVENTION

[0007] However, with the first type of conventional hybrid vehicle, forexample, it becomes necessary to limit the regenerative torque whenoverheating occurs when the electrical energy is generated by the drivemotor. However, the drive motor torque that corresponds to the amount ofthe engine torque in excess of the vehicle requirement torque cannot beabsorbed by the regenerative torque. In this case, an engine torquegreater than the vehicle requirement torque is transmitted to the drivewheel, thereby imparting an unpleasant sensation to a driver.

[0008] Furthermore, in the second type of hybrid vehicle, if an amountof engine torque is attempted to be absorbed as regenerative torque in ahigh vehicle speed zone, like the engine, the drive motor is made torotate at a high rotational speed. The drive motor thus cannotadequately absorb the regenerative torque. As a result, it is necessaryto limit the regenerative torque. However in this case, an engine torquegreater than the vehicle requirement torque is transmitted to the drivewheel, and thus an unpleasant sensation is imparted to a driver.

[0009] Further, in the above-mentioned second type of hybrid vehicle,there is a case where, for example, the hybrid vehicle is drivenbackward while the engine is running and the generator is generatingpower. If it becomes necessary to limit drive motor torque for somereason, the drive motor torque in the reverse direction which issufficient to overpower the engine torque cannot be generated. Thismakes it difficult to move the hybrid vehicle backward, and as a result,an uncomfortable sensation is imparted to a driver.

[0010] The invention thus solves the problems of the aforementionedconventional hybrid vehicles, and provides a hybrid vehicle drivecontrol device that does not impart an unpleasant sensation to a driverwhen it becomes necessary to limit drive motor torque, a hybrid vehicledrive control method and a program thereof.

[0011] For this purpose, the hybrid vehicle control device according toan exemplary aspect of the invention includes a motor that compensatesfor an excessive or a deficient amount of engine torque with respect toa vehicle requirement torque and a controller that detects a torquelimit index, which is an index that limits a drive motor torque,determines whether the torque limit index has exceeded a thresholdvalue, limits the drive motor torque when the torque limit index hasexceeded the threshold value, and adjusts the engine torque, inaccordance with a limiting of the drive motor torque.

[0012] In this case, when the torque limit index has exceeded thethreshold value and it has become necessary to limit the drive motortorque, the engine torque is adjusted and reduced by that amount.Therefore, the unpleasant sensation is not imparted to the driverbecause an engine torque greater than the vehicle requirement torque isnot transmitted to the drive wheel.

[0013] According to an embodiment of the invention, the drive motortorque required to move the hybrid vehicle backward when the reverserange is selected is limited. As the drive motor torque is limited, theengine torque is adjusted.

[0014] According to another embodiment of the invention, it is possibleto generate a drive motor torque in a reverse direction such that it issufficient to overpower the engine output. This makes it easy to drivethe hybrid vehicle backward, and a driver does not have an unpleasantsensation.

[0015] In a hybrid vehicle control method according to the invention,the method includes detecting a torque limit index, which is an indexthat limits a drive motor torque of a drive motor that compensates foran excessive or a deficient amount of engine torque with respect to avehicle requirement torque vehicle, determining whether the torque limitindex has exceeded a threshold value, limiting the drive motor torquewhen the torque limit index has exceeded the threshold value, andadjusting the engine torque in accordance with the limiting of the drivemotor torque.

[0016] A program of the hybrid vehicle drive control apparatus includesa routine that determines whether a torque limit index has exceeded athreshold value, a routine that limits a drive motor torque when thetorque limit index has exceeded the threshold value, and a routine thatadjusts an engine torque in accordance with the limiting of the drivemotor torque.

BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Various embodiments of the invention will be described withreference to the drawings, wherein

[0018]FIG. 1 is a function block diagram of a hybrid vehicle drivecontrol device according to a first embodiment of the invention;

[0019]FIG. 2 is a conceptual diagram of a hybrid vehicle according tothe first embodiment of the invention;

[0020]FIG. 3 is an operation explanatory diagram of a planetary gearunit according to the first embodiment of the invention;

[0021]FIG. 4 is a diagram of vehicle speed during normal running periodsaccording to the first embodiment of the invention;

[0022]FIG. 5 is a diagram of torque during normal running periodsaccording to the first embodiment of the invention;

[0023]FIG. 6 is a conceptual diagram of a hybrid vehicle drive controldevice according to the first embodiment of the invention;

[0024]FIG. 7 is a first main flow chart illustrating an operation of ahybrid vehicle drive control device according to the first embodiment ofthe invention;

[0025]FIG. 8 is a second main flow chart illustrating the operation ofthe hybrid vehicle drive control device according to the firstembodiment of the invention;

[0026]FIG. 9 is a third main flow chart illustrating the operation ofthe hybrid vehicle drive control device according to the firstembodiment of the invention;

[0027]FIG. 10 is a drawing illustrating a first vehicle requirementtorque map according to the first embodiment of the invention;

[0028]FIG. 11 is a drawing illustrating a second vehicle requirementtorque map according to the first embodiment of the invention;

[0029]FIG. 12 is a drawing illustrating an engine target operation statemap according to the first embodiment of the invention;

[0030]FIG. 13 is a drawing illustrating an engine drive area mapaccording to the first embodiment of the invention;

[0031]FIG. 14 is a drawing illustrating a subroutine of a suddenacceleration control process according to the first embodiment of theinvention;

[0032]FIG. 15 is a drawing illustrating a subroutine of a drive motorcontrol process according to the first embodiment of the invention;

[0033]FIG. 16 is a drawing illustrating a subroutine of a generatortorque control process according to the first embodiment of theinvention;

[0034]FIG. 17 is a drawing illustrating a subroutine of an engine startcontrol process according to the first embodiment of the invention;

[0035]FIG. 18 is a drawing illustrating a subroutine of a generatorrotational speed control process according to the first embodiment ofthe invention;

[0036]FIG. 19 is a drawing illustrating a subroutine of an engine stopcontrol process according to the first embodiment of the invention;

[0037]FIG. 20 is a drawing illustrating a subroutine of a generatorbrake engage control process according to the first embodiment of theinvention;

[0038]FIG. 21 is a drawing illustrating a subroutine of a generatorbrake release control process according to the first embodiment of theinvention;

[0039]FIG. 22 is a drawing illustrating a limiting method for drivemotor target torque according to the first embodiment of the invention;

[0040]FIG. 23 is a drawing illustrating a subroutine of an enginecontrol process according to the first embodiment of the invention;

[0041]FIG. 24 is a first time chart illustrating an operation of theengine control process according to the first embodiment of theinvention;

[0042]FIG. 25 is a second time chart illustrating the operation of theengine control process according to the first embodiment of theinvention;

[0043]FIG. 26 is a drawing illustrating a subroutine of an enginecontrol process according to a second embodiment of the invention;

[0044]FIG. 27 is a time chart illustrating the operation of the enginecontrol process according to the second embodiment of the invention; and

[0045]FIG. 28 is a drawing illustrating a subroutine of an enginecontrol process according to a third embodiment of the invention.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

[0046] Hereafter, embodiments of the invention are described in detailwith reference to the accompanying drawings. FIG. 1 is a function blockdiagram of a hybrid vehicle drive control device according to a firstembodiment of the invention. In the drawing, reference numeral 25denotes a drive motor that compensates for an excessive or a deficientamount of torque of an engine (not shown), i.e., the engine torque, withrespect to a vehicle requirement torque required by a hybrid vehicle.Reference numeral 65 denotes a drive motor temperature sensor, whichfunctions as a torque limit index detection portion that detects atorque limit index, which is an index that limits a torque of the drivemotor 25, i.e., the drive motor torque. Reference numeral 91 denotes anindex determination processing mechanism that determines whether thetorque limit index has exceeded a threshold value; reference numeral 92denotes a torque limit processing mechanism that limits the drive motortorque when the torque limit index has exceeded the threshold value;reference numeral 93 denotes an engine torque adjustment processingmechanism that adjusts the engine torque, in accordance with thelimiting of the drive motor torque.

[0047] Next, the hybrid vehicle will be described. Note that in thiscase, the description refers to the second type of hybrid vehicle asdescribed earlier, but the invention is also applicable to the firsttype of hybrid vehicle. FIG. 2 is a conceptual diagram of a hybridvehicle according to the first embodiment of the invention.

[0048] In the drawing, reference numeral 11 denotes an engine (E/G)provided on a first axis; reference numeral 12 denotes an output shaftprovided on the first axis that outputs rotation generated by the driveof the engine 11; reference numeral 13 denotes a planetary gear unitprovided on the first axis which is a differential gear unit that shiftswith regard to a rotation input via the output shaft 12; referencenumeral 14 denotes an output shaft provided on the first axis thatoutputs the rotation after shifting the planetary gear unit 13;reference numeral 15 denotes a first counter drive gear which is anoutput gear fixed to the output shaft 14; reference numeral 16 denotes agenerator (G), provided on the first axis, which is a first electricmachine that is connected with the planetary gear unit 13 via a transfershaft 17 and is further mechanically connected with the engine 11 in amanner allowing differential rotation.

[0049] The output shaft 14 has a sleeve shape and is provided encirclingthe output shaft 12. Also, the first counter drive gear 15 is providedcloser to the engine 11 side than the planetary gear unit 13.

[0050] The planetary gear unit 13 is equipped with at least a sun gear Swhich is a first gear element, a pinion P that meshes with the sun gearS, a ring gear R which is a second gear element that meshes with thepinion P, and a carrier CR which is a third gear element that rotatablysupports the pinion P. The sun gear S is connected with the generator 16via the transfer shaft 17, the ring gear R is connected, via the outputshaft 14 and a predetermined gear train, with a drive wheel 37 and thedrive motor (M) 25 which is a second electric machine, and the carrierCR is connected with the engine 11 via the output shaft 12. Furthermore,the drive motor 25 is provided on a second axis parallel to the firstaxis, and is mechanically connected with the engine 11 and the generator16 in a manner allowing differential rotation, and is mechanicallyconnected with the drive wheel 37. Also, a one-way clutch F is providedbetween the carrier CR and a case 10 of a hybrid vehicle drive device,which is a vehicle drive device. The one-way clutch F becomes free whenforward rotation from the engine 11 is transmitted to the carrier CR,and locked when reverse rotation from the generator 16 or the drivemotor 25 is transmitted to the carrier CR, so that the reverse rotationis not transmitted to the engine 11.

[0051] The generator 16 is fixed to the transfer shaft 17 and includes arotor 21 that is provided rotatably, a stator 22 that is provided aroundthe rotor 21, and a coil 23 that is wound around the stator 22. Thegenerator 16 generates electric power through the rotation transmittedvia the transfer shaft 17. The coil 23 is connected to a battery (notshown), and alternating current from the coil 23 is converted to directcurrent and supplied to the battery. A generator brake B is providedbetween the rotor 21 and the case 10, and by engaging the generatorbrake B, the rotor 21 is fixed and the rotation of the generator 16 canbe mechanically stopped.

[0052] In addition, reference numeral 26 denotes an output shaftprovided on the second axis that outputs the rotation of the drive motor25, and reference numeral 27 denotes a second counter drive gear whichis an output gear that is fixed to the output shaft 26. The drive motor25 includes a rotor 40 that is fixed to the output shaft 26 and providedrotatably, a stator 41 that is provided around the rotor 40, and a coil42 that is wound around the stator 41.

[0053] The drive motor 25 generates a drive motor torque TM through thephase U, V, and W electric currents that are alternating currentssupplied to the coil 42. Therefore, the coil 42 is connected to thebattery, so that the direct current from the battery is converted intoelectric current of each phase and supplied to the coil 42.

[0054] In order to rotate the drive wheel 37 in the same direction ofrotation as the engine 11, a counter shaft 30 is provided on a thirdaxis parallel to the first and second axes. Furthermore, a first counterdriven gear 31 and a second counter driven gear 32 that has more teeththan the first counter driven gear 31 are fixed to the counter shaft 30.The first counter driven gear 31 and the first counter drive gear 15,and the second counter driven gear 32 and the second counter drive gear27 are meshed respectively, such that the rotation of the first counterdrive gear 15 is reversed, so as to be transmitted to the first counterdriven gear 31 and the rotation of the second counter drive gear 27 isreversed so as to be transmitted to the second counter driven gear 32.Furthermore, a differential pinion gear 33 that has fewer teeth than thefirst counter driven gear 31 is fixed to the counter shaft 30.

[0055] A differential device 36 is provided on a fourth axis parallel tothe first, second, and third axes, and a differential ring gear 35 ofthe differential device 36 is meshed with the differential pinion gear33. Accordingly, rotation transmitted to the differential ring gear 35is distributed and transmitted to the drive wheel 37 by the differentialdevice 36. Thus, not only can rotation generated by the engine 11 betransmitted to the first counter driven gear 31, but rotation generatedby the drive motor 25 can also be transmitted to the second counterdriven gear 32. Therefore the hybrid vehicle is capable of running onthe drive of both the engine 11 and the drive motor 25.

[0056] In this case, reference numeral 38 denotes a generator rotorposition sensor such as a resolver that detects the position of therotor 21, i.e., a generator rotor position θG, and reference numeral 39denotes a drive motor rotor position sensor such as a resolver thatdetects the position of the rotor 40, i.e., a drive motor rotor positionθM. The detected generator rotor position θG is sent to a vehiclecontrol device (not shown) and a generator control device (not shown).The drive motor rotor position θM is sent to the vehicle control deviceand a drive motor control device (not shown). Furthermore, referencenumeral 52 denotes an engine rotational speed sensor which is an enginerotational speed detection mechanism that detects a rotational speed ofthe engine 11, i.e., an engine rotational speed NE.

[0057] Next, the operation of the planetary gear unit 13 will bedescribed. FIG. 3 is an operation explanatory diagram of a planetarygear unit according to the first embodiment of the invention, and FIG. 4is a diagram of vehicle speed during normal running periods according tothe first embodiment of the invention. FIG. 5 is a diagram of torqueduring normal running periods according to the first embodiment of theinvention.

[0058] In the planetary gear unit 13 (FIG. 2), the carrier CR isconnected with the engine 11, the sun gear S is connected with thegenerator 16, and the ring gear R is connected with the drive motor 25and the drive wheel 37 respectively via the output shaft 14. Therefore,a rotational speed of the ring gear R, i.e., a ring gear rotationalspeed NR, and a rotational speed output to the output shaft 14, i.e., anoutput shaft rotational speed are equal, and a rotational speed of thecarrier CR and the engine rotational speed NE are equal. Furthermore, arotational speed of the sun gear S and a rotational speed of thegenerator 16, i.e., a generator rotational speed NG become equal. Whenthe number of teeth of the ring gear R is p times the number of teeth ofthe sun gear S (two times in the embodiment), the relationship,

(ρ+1)·NE=1·NG+ρ·NR

[0059] is established. Accordingly, based on the ring gear rotationalspeed NR and the generator rotational speed NG, the engine rotationalspeed NE,

NE=(1·NG+ρ·NR)/(ρ+1)   (1)

[0060] can be calculated. In this case, the rotational speed relationalexpression of the planetary gear unit 13 is constructed according toformula (1).

[0061] In addition, an engine torque TE, a torque generated by the ringgear R, i.e., a ring gear torque TR, and a torque of the generator 16,i.e., a generator torque TG, have the relationship,

TE:TR:TG=(ρ+1):ρ:1   (2)

[0062] and receive reaction forces from each other. In this case, thetorque relational expression of the planetary gear unit 13 isconstructed according to formula (2).

[0063] During a normal running period of the hybrid vehicle, each of thering gear R, the carrier CR, and the sun gear S are rotated in thepositive direction, and as shown in FIG. 4, each of the ring gearrotational speed NR, the engine rotational speed NE, and the generatorrotational speed NG assumes a positive value. In addition, the ring geartorque TR and the generator torque TG are obtained by proportionallydividing the engine torque TE by the torque ratio determined by thenumber of teeth in the planetary gear unit 13. Therefore, in the torquediagram shown in FIG. 5, the sum of the ring gear torque TR and thegenerator torque TG becomes the engine torque TE.

[0064] Next, the hybrid vehicle drive control device, which is anelectric vehicle drive control device, that controls the hybrid vehicledrive device will be described. FIG. 6 is a conceptual diagram of ahybrid vehicle drive control device according to the first embodiment ofthe invention.

[0065] In the drawing, reference numeral 10 denotes the case; referencenumeral 11 denotes the engine (E/G); reference numeral 13 denotes theplanetary gear unit; reference numeral 16 denotes the generator (G);reference symbol B denotes the generator brake for fixing the rotor 21of the generator 16; reference numeral 25 denotes the drive motor (M);reference numeral 28 denotes an inverter which is a generator inverterfor driving the generator 16; reference numeral 29 denotes an inverterwhich is a drive motor inverter for driving the drive motor 25;reference numeral 37 denotes the drive wheel; reference numeral 38denotes the generator rotor position sensor; reference numeral 39denotes the drive motor rotor position sensor; and reference numeral 43denotes the battery. The inverters 28 and 29 are connected to thebattery 43 via a power switch SW, and when the power switch SW is on,the battery 43 supplies a direct current to the inverters 28 and 29.

[0066] On the input port side of the inverter 28, a generator invertervoltage sensor 75 which is a first direct current voltage detectionportion for detecting a direct current voltage applied to the inverter28, i.e., a generator inverter voltage VG, and a generator inverterelectric current sensor 77 which is a first direct current detectionportion for detecting a direct current supplied to the inverter 28,i.e., a generator inverter electric current IG, are provided. Inaddition, the input port side of the inverter 29 is provided with adrive motor inverter voltage sensor 76 which is a second direct currentvoltage detection portion for detecting a direct current voltage appliedto the inverter 29, i.e., a drive motor inverter voltage VM, and a drivemotor inverter electric current sensor 78 which is a second directcurrent detection portion for detecting a direct current supplied to theinverter 29, i.e., a drive motor inverter electric current IM. Thegenerator inverter voltage VG and the generator inverter electriccurrent IG are sent to a vehicle control device 51 and a generatorcontrol device 47, while the drive motor inverter voltage VM and thedrive motor inverter electric current IM are sent to the vehicle controldevice 51 and a drive motor control device 49. A smoothing capacitor Cis connected between the battery 43 and the inverters 28 and 29.

[0067] Also, the vehicle control device 51 includes a CPU, recordingequipment, and the like (not shown), controls the entire hybrid vehicledrive control device, and functions as a computer based on variousprograms, data, and the like. An engine control device 46, the generatorcontrol device 47, and the drive motor control device 49 are connectedto the vehicle control device 51. The engine control device 46 includesa CPU, recording equipment, and the like (not shown), and sends commandsignals such as throttle opening 0 and valve timing to the engine 11 inorder to control the engine 11. The generator control device 47 includesa CPU, recording equipment, and the like (not shown), and sends a drivesignal SG1 to the inverter 28 in order to control the generator 16.Furthermore, the drive motor control device 49 includes a CPU, recordingequipment, and the like (not shown), and sends a drive signal SG2 to theinverter 29 in order to control the drive motor 25. In this case, theengine control device 46, the generator control device 47, and the drivemotor control device 49 constitute a first control device that issubordinate to the vehicle control device 51, and the vehicle controldevice 51 constitutes a second control device that is superordinate tothe engine control device 46, the generator control device 47, and thedrive motor control device 49. In addition, the engine control device46, the generator control device 47, and the drive motor control device49 also function as computers based on various programs, data, and thelike.

[0068] The inverter 28 is driven according to the drive signal SG1, andreceives a direct current from the battery 43 during powering, therebygenerating the electric current IGU, IGV, and IGW of each phase, andsupplying the electric current IGU, IGV, and IGW of each phase to thegenerator 16. During regeneration, the inverter 28 receives the electriccurrent IGU, IGV, and IGW of each phase from the generator 16, andgenerates a direct current which is supplied to the battery 43.

[0069] Furthermore, the inverter 29 is driven according to the drivesignal SG2, and receives a direct current from the battery 43 duringpowering, thereby generating electric current IMU, IMV, and IMW of eachphase, and supplying the electric current IMU, IMV, and IMW of eachphase to the drive motor 25. During regeneration, the inverter 29receives the electric current IMU, IMV, and IMW of each phase from thedrive motor 25, and generates a direct current which is supplied to thebattery 43.

[0070] Furthermore, reference numeral 44 denotes a battery remainingcharge detection device that detects a state of the battery 43, i.e., abattery remaining charge SOC which is a battery state; reference numeral52 denotes the engine rotational speed sensor; reference numeral 53denotes a shift position sensor that detects the position of a shiftlever (not shown) which is a speed selecting operation mechanism, i.e.,a shift position SP; reference numeral 54 denotes an accelerator pedal;reference numeral 55 denotes an accelerator switch which is anaccelerator operation detection portion that detects a position (amountof depression) of the accelerator pedal 54, i.e., an accelerator pedalposition AP; reference numeral 61 denotes a brake pedal; referencenumeral 62 denotes a brake switch which is a brake operation detectionportion that detects a position (amount of depression) of the brakepedal 61, i.e., a brake pedal position BP; reference numeral 63 denotesan engine temperature sensor that detects a temperature tmE of theengine 11; reference numeral 64 denotes a generator temperature sensorthat detects a temperature of the generator 16, for example, atemperature tmG of the coil 23; reference numeral 65 denotes the drivemotor temperature sensor which is a torque limit index detection portionand a temperature detection portion that detects a temperature of thedrive motor 25, for example, a temperature tmM of the coil 42.

[0071] Furthermore, reference numerals 66 to 69 denote electric currentsensors which are alternating electric current detection portions thatdetect electric currents, IGU, IGV, IMU, and IMV of each phase, andreference numeral 72 denotes a battery voltage sensor which is a voltagedetection portion for the battery 43 that detects a battery voltage VBwhich is a battery state. The battery voltage VB is sent to thegenerator control device 47, the drive motor control device 49, and thevehicle control device 5 1. In addition, battery electric current,battery temperature, and the like may be detected as battery states. Thebattery remaining charge detection device 44, the battery voltage sensor72, a battery electric current sensor (not shown), a battery temperaturesensor (not shown), and the like constitute a battery state detectionportion. Also, the electric currents IGU and IGV are supplied to thegenerator control device 47 and the vehicle control device 5 1, whilethe electric currents IMU and IMV are supplied to the drive motorcontrol device 49 and the vehicle control device 51.

[0072] The vehicle control device 51 sends an engine control signal tothe engine control device 46 so as to cause the engine control device 46to set the starting and stopping of the engine 11. Furthermore, avehicle speed calculation processing mechanism (not shown) of thevehicle control device 51 executes a vehicle speed calculation processto calculate a changing rate ΔθM of the drive motor rotor position θM,and calculates the vehicle speed V based on the changing rate ΔθM and agear ratio γV of the torque transmission system from the output shaft 26to the drive wheel 37.

[0073] Then, the vehicle control device 51 sets an engine targetrotational speed NE* that indicates a target value for the enginerotational speed NE, a generator target torque TG* that indicates atarget value of the generator torque TG, and a drive motor target torqueTM* that indicates a target value of the drive motor torque TM. Thegenerator control device 47 sets a generator target rotational speed NG*that indicates a target value for the generator rotational speed NG, andthe drive motor control device 49 sets a drive motor torque compensationvalue δTM that indicates a compensation value of the drive motor torqueTM. In this case, a control command value is constituted by the enginetarget rotational speed NE*, the generator target torque TG*, the drivemotor target torque TM*, and the like.

[0074] In addition, a generator rotational speed calculation processingmechanism (not shown) of the generator control device 47 executes agenerator rotational speed calculation process to calculate thegenerator rotational speed NG, by reading the generator rotor positionθG and calculating a changing rate ΔθG of the generator rotor positionθG.

[0075] Furthermore, a drive motor rotational speed calculationprocessing mechanism (not shown) of the drive motor control device 49executes a drive motor rotational speed calculation process to calculatethe rotational speed of the drive motor 25, i.e., the drive motorrotational speed NM, by reading the drive motor rotor position θM andcalculating a changing rate ΔθM of the drive motor rotor position θM.

[0076] Since the generator rotor position θG and the generatorrotational speed NG are proportionate to each other, and the drive motorrotor position θM, the drive motor rotational speed NM, and the vehiclespeed V are all proportionate to each other, the generator rotorposition sensor 38 and the generator rotational speed calculationprocessing mechanism can function as a generator rotational speeddetection portion that detects the generator rotational speed NG. Also,the drive motor rotor position sensor 39 and the drive motor rotationalspeed calculation processing mechanism can function as a drive motorrotational speed detection portion that detects the drive motorrotational speed NM. Furthermore, the drive motor rotor position sensor39 and the vehicle speed calculation processing mechanism can functionas a vehicle speed detection portion that detects the vehicle speed V.

[0077] In the embodiment, the engine rotational speed NE is detected bythe engine rotational speed sensor 52, however, the engine rotationalspeed NE can also be calculated in the engine control device 46. Also,in the embodiment, the vehicle speed V is calculated by the vehiclespeed calculation processing mechanism based on the drive motor rotorposition θM. However, the vehicle speed V can also be calculated basedon the detected ring gear rotational speed NR, or based on a rotationalspeed of the drive wheel 37, i.e., a drive wheel rotational speed. Inthis case, a ring gear rotational speed sensor, a drive wheel rotationalspeed sensor or the like are provided as a vehicle speed detectionportion.

[0078] Next, an operation of a hybrid vehicle drive control device ofthe aforementioned structure will be described. FIG. 7 is a first mainflow chart illustrating the operation of the hybrid vehicle drivecontrol device according to the first embodiment of the invention; FIG.8 is a second main flow chart illustrating the operation of the hybridvehicle drive control device according to the first embodiment of theinvention; FIG. 9 is a third main flow chart illustrating the operationof the hybrid vehicle drive control device according to the firstembodiment of the invention; FIG. 10 is a drawing illustrating a firstvehicle requirement torque map according to the first embodiment of theinvention; FIG. 11 is a drawing illustrating a second vehiclerequirement torque map according to the first embodiment of theinvention; FIG. 12 is a drawing illustrating an engine target operationstate map according to the first embodiment of the invention; and FIG.13 is a drawing illustrating an engine drive area map according to thefirst embodiment of the invention. In FIGS. 10, 11, and 13, the x-axisis the vehicle speed V and the y-axis is a vehicle requirement torqueTO*. In FIG. 12, the x-axis is the engine rotational speed NE, and they-axis is the engine torque TE.

[0079] First, an initialization processing mechanism (not shown) of thevehicle control device 51 (FIG. 6) executes an initialization process toset each type of variable to a default value. Next, the vehicle controldevice 51 reads the accelerator pedal position AP from the acceleratorsensor 55 and the brake pedal position BP from the brake switch 62.Then, the vehicle speed calculation processing mechanism reads the drivemotor rotor position θM, calculates the changing rate ΔθM of the drivemotor rotor position θM, and then calculates the vehicle speed V basedon the changing rate ΔθM and the gear ratio γV.

[0080] Subsequently, a vehicle requirement torque determinationprocessing mechanism (not shown) of the vehicle control device 51executes the vehicle requirement torque determination process. When theaccelerator pedal 54 is pressed, the vehicle control device 51 refers tothe first vehicle requirement torque map in FIG. 10 which is recorded inthe recording equipment of the vehicle control device 51. When the brakepedal 61 is pressed, the vehicle control device 51 refers to the secondvehicle requirement torque map in FIG. 11 which is recorded in therecording equipment. The vehicle control device 51 thus determines thenecessary vehicle requirement torque TO* for running the hybrid vehiclewhich is preset to correspond with the accelerator pedal position AP,the brake pedal position BP, and the vehicle speed V.

[0081] Next, the vehicle control device 51 determines whether thevehicle requirement torque TO* is greater than a drive motor maximumtorque TMmax that is preset as the rating of the drive motor 25. If thevehicle requirement torque TO* is greater than the drive motor maximumtorque TMmax, then the vehicle control device 51 determines whether theengine 11 is stopped. If the engine 11 is stopped, then a suddenacceleration control processing mechanism (not shown) of the vehiclecontrol device 51 executes a sudden acceleration control process,thereby driving the drive motor 25 and the generator 16 to run thehybrid vehicle.

[0082] Also, when the vehicle requirement torque TO* is equal to or lessthan the drive motor maximum torque TMmax, or the vehicle requirementtorque TO* is greater than the drive motor maximum torque TMmax and theengine 11 is being driven, a driver requirement output calculationprocessing mechanism (not shown) of the vehicle control device 51executes a driver requirement output calculation process to calculate adriver requirement output PD by multiplying the vehicle requirementtorque TO* by the vehicle speed V:

PD=TO*·V

[0083] Next, a battery charge/discharge requirement output calculationprocessing mechanism (not shown) of the vehicle control device 51executes a battery charge/discharge requirement output calculationprocess to calculate a battery charge/discharge requirement output PBbased on the battery remaining charge SOC by reading the batteryremaining charge SOC from the battery remaining charge detection device44.

[0084] Thereafter, a vehicle requirement output calculation processingmechanism (not shown) of the vehicle control device 51 executes avehicle requirement output calculation process, and by adding the driverrequirement output PD and the battery charge/discharge requirementoutput PB, calculates a vehicle requirement output PO:

PO=PD+PB

[0085] Next, an engine target operation state setting processingmechanism (not shown) of the vehicle control device 51 executes anengine target operation state setting process, and refers to the enginetarget operation state map in FIG. 12 which is recorded in the recordingequipment of the vehicle control device 51 to determine as operationpoints of the engine 11 which are engine target operation states, thepoints A1 to A3, and Am at which the lines PO1, P02, and the like whichindicate whether the vehicle requirement output PO intersects theoptimum fuel consumption curve L where the engine 11 reaches maximumefficiency at each accelerator pedal position AP1 to AP6. Then, enginetorque TE1 to TE3, and TEm at the operation point are determined as theengine target torque TE* which indicates the target value of the enginetorque TE, and engine rotational speeds NE1 to NE3, and NEm at theoperation point are determined as the engine target rotational speedNE*. Thereafter, the engine target rotational speed NE* is sent to theengine control device 46.

[0086] Then, the engine control device 46 refers to the engine drivearea map in FIG. 13 which is recorded in the recording equipment of theengine control device 46 and determines whether the engine 11 is in adrive area AR1. In FIG. 13, AR1 is a drive area where the engine 11 isdriven, AR2 is a stop area where the drive of the engine 11 is stopped,and AR3 is a hysteresis area. Furthermore, LE1 is a line where thestopped engine 11 is driven, and LE2 is a line where the drive of thedriving engine 11 is stopped. As the battery remaining charge SOCbecomes higher, the line LE1 is shifted to the right in FIG. 13, and thedrive area AR1 becomes more narrow. On the other hand, as the batteryremaining charge SOC becomes lower, the line LE1 is shifted to the leftin FIG. 13, and the drive area AR1 becomes wider.

[0087] If the engine 11 is not being driven despite the engine 11 beingin the drive area AR1, an engine start control processing mechanism (notshown) of the engine control device 46 executes an engine start controlprocess and causes the engine 11 to start. On the other hand, if theengine 11 is being driven despite the engine 11 not being in the drivearea AR1, an engine stop control processing mechanism (not shown) of theengine control device 46 executes an engine stop control process andstops the drive of the engine 11. Furthermore, if the engine 11 is notbeing driven with the engine 11 not in the drive area AR1, a drive motortarget torque calculation processing mechanism (not shown) of thevehicle control device 51 executes a drive motor target torquecalculation process to calculate and determine the vehicle requirementtorque TO* as the drive motor target torque TM*, and sends the drivemotor target torque TM* to the drive motor control device 49. The drivemotor control processing mechanism (not shown) of the drive motorcontrol device 49 executes a drive motor control process and controlsthe torque of the drive motor 25.

[0088] In addition, when the engine 11 is in the drive area AR1 and theengine 11 is being driven, an engine control processing mechanism (notshown) of the engine control device 46 executes an engine controlprocess and controls the engine 11 by a predetermined method.

[0089] Next, a generator target rotational speed calculation processingmechanism (not shown) of the generator control device 47 executes agenerator target rotational speed calculation process. Specifically, thedrive motor rotor position OM is read from the drive motor rotorposition sensor 39, and the ring gear rotational speed NR is calculatedbased on the drive motor rotor position θM and a gear ratio γR from theoutput shaft 26 (FIG. 2) to the ring gear R. Also, the engine targetrotational speed NE* set through the engine target operation statesetting process is read, and the generator target rotational speed NG*is calculated and determined, using the rotational speed relationalexpression, based on the ring gear rotational speed NR and the enginetarget rotational speed NE*.

[0090] Meanwhile, when the generator rotational speed NG is low whilethe engine 11 and the motor 25 are driven to run the hybrid vehicle,power consumption increases, thereby reducing the power generationefficiency of the generator 16 and causing the fuel efficiency of thehybrid vehicle to become that much worse. Therefore, when the absolutevalue of the generator target rotational speed NG* is smaller than apredetermined rotational speed, the generator brake B is engaged,thereby mechanically stopping the generator 16 so as to improve fuelefficiency.

[0091] For that purpose, the generator control device 47 determineswhether the absolute value of the generator target rotational speed NG*is equal to or higher than a predetermined first rotational speed Nth1(for example, 500 [rpm]). If the absolute value of the generator targetrotational speed NG* is equal to or higher than the first rotationalspeed Nth1, the generator control device 47 determines whether thegenerator brake B is released. Then, if the generator brake B isreleased, a generator rotational speed control processing mechanism (notshown) of the generator control device 47 executes a generatorrotational speed control process and controls the torque of thegenerator 16. On the other hand, if the generator brake B has not beenreleased, a generator brake release control processing mechanism (notshown) of the generator control device 47 executes a generator brakerelease control process and releases the generator brake B.

[0092] Meanwhile, in the generator rotational speed control process,when a predetermined generator torque TG is generated after thegenerator target torque TG* is determined and the torque of thegenerator 16 is controlled based on the generator target torque TG*, asdescribed earlier, the engine torque TE, the ring gear torque TR, andthe generator torque TG will receive reaction forces from each other,therefore, the generator torque TG is converted into the ring geartorque TR to be output from the ring gear R.

[0093] Then, if fluctuations in the generator rotational speed NG occursalong with the ring gear torque TR output from the ring gear R, and thering gear torque TR fluctuates, the fluctuating ring gear torque TR istransmitted to the drive wheel 37 which deteriorates the running feelingof the hybrid vehicle. Therefore, the ring gear torque TR is calculatedtaking into account the torque corresponding to the inertia of thegenerator 16 (inertia of the rotor 21 and a rotor shaft) involved in thefluctuations of the generator rotational speed NG.

[0094] For that purpose, a ring gear torque calculation processingmechanism (not shown) of the vehicle control device 51 executes a ringgear torque calculation process, reads the generator target torque TG*,and calculates the ring gear torque TR based on the generator targettorque TG* and the ratio of the number of ring gear R teeth to thenumber of sun gear S teeth.

[0095] Namely, when InG is the inertia of the generator 16 and αG is theangular acceleration (rotation changing rate) of the generator 16,torque applied to the sun gear S, i.e., a sun gear torque TS is obtainedby adding a torque equivalent component (inertia torque) TGIcorresponding to the inertia InG to the generator target torque TG*,

TGI=InG·aα

[0096] thereby becoming: $\begin{matrix}\begin{matrix}{{TS} = {{TG}^{*} + {TGI}}} \\{= {{TG}^{*} + {{{InG} \cdot \alpha}\quad G}}}\end{matrix} & (3)\end{matrix}$

[0097] The torque equivalent component TGI usually assumes a negativevalue in the direction of acceleration while the hybrid vehicle isaccelerating and assumes a positive value in the direction ofacceleration when the hybrid vehicle is decelerating. Also, the angularacceleration αG is calculated by differentiating the generatorrotational speed NG.

[0098] When the number of ring gear R teeth is ρ times greater than thenumber of sun gear S teeth, the ring gear torque TR is ρ times the sungear torque TS, therefore TR becomes: $\begin{matrix}\begin{matrix}{{TR} = {\rho \cdot {TS}}} \\{= {\rho \cdot ( {{TG}^{*} + {TGI}} )}} \\{= {\rho \cdot ( {{TG}^{*} + {{{InG} \cdot \alpha}\quad G}} )}}\end{matrix} & (4)\end{matrix}$

[0099] As shown above, the ring gear torque TR can be calculated fromthe generator target torque TG* and the torque equivalent component TGI.

[0100] Therefore, a drive shaft torque estimation processing mechanism(not shown) of the drive motor control device 49 executes a drive shafttorque estimation process, and estimates a torque of the output shaft26, i.e., a drive shaft torque TR/OUT, based on the generator targettorque TG* and the torque equivalent component TGI. Namely, the driveshaft torque estimation processing mechanism estimates and calculatesthe drive shaft torque TR/OUT based on the ring gear torque TR and theratio of the number of second counter drive gear 27 teeth to the numberof ring gear R teeth.

[0101] Meanwhile, at the time the generator brake B is engaged, thegenerator target torque TG* becomes zero (0), therefore the ring geartorque TR takes on a proportional relationship with the engine torqueTE. So when the generator brake B is engaged, the drive shaft torqueestimation processing mechanism reads the engine torque TE from theengine control device 46, calculates the ring gear torque TR based onthe engine torque TE using the aforementioned torque relationalexpression, and estimates the drive shaft torque TR/OUT based on thering gear torque TR and the ratio of the number of second counter drivegear 27 teeth to the number of ring gear R teeth.

[0102] Subsequently, the drive motor target torque calculationprocessing mechanism executes a drive motor target torque calculationprocess, and by subtracting the drive shaft torque TR/OUT from thevehicle requirement torque TO*, calculates and determines the excessiveor deficient amount of torque in the drive shaft torque TR/OUT as thedrive motor target torque TM*.

[0103] Then, the drive motor control processing mechanism executes adrive motor control process, and controls the torque of the drive motor25 based on the determined drive motor target torque TM* to control thedrive motor torque TM.

[0104] In addition, when the absolute value of the generator targetrotational speed NG* is smaller than the first rotational speed Nth1,the generator control device 47 determines whether the generator brake Bis engaged. If the generator brake B is not engaged, then a generatorbrake engage control processing mechanism (not shown) of the generatorcontrol device 47 executes a generator brake engage control process andengages the generator brake B.

[0105] Next, the flow charts of FIGS. 7 to 9 will be described. In stepS1, an initialization process is executed, in step S2, the acceleratorpedal position AP and the brake pedal position BP are read, in step S3,the vehicle speed V is calculated and in step S4, the vehiclerequirement torque TO* is determined.

[0106] In step S5, a determination is made as to whether the vehiclerequirement torque TO* is greater than the drive motor maximum torqueTMmax. If the vehicle requirement torque TO* is greater than the drivemotor maximum torque TMmax, the operation proceeds to step S6. If thevehicle requirement torque TO* is equal to or less than the drive motormaximum torque TMmax, the operation proceeds to step S8. In step S6, adetermination is made as to whether the engine 11 is stopped. If theengine 11 is stopped, the operation proceeds to step S7 where the suddenacceleration control process is executed and the process ends.Otherwise, if the engine is not stopped, the operation proceeds to stepS8.

[0107] In step S8, the driver requirement output PD is calculated, instep S9, the battery charge/discharge requirement output PB iscalculated, in step S10, the vehicle requirement output PO is calculatedand in step S11, the operation point of the engine 11 is determined.

[0108] In step S12, a determination is made as to whether the engine 11is in the drive area AR1. If the engine 11 is in the drive area AR1, theoperation proceeds to step S13. Otherwise, the operation proceeds tostep S14. In step S13, a determination is made as to whether the engine11 is being driven. If the engine 11 is being driven, the operationproceeds to step S17. Otherwise, the operation proceeds to step S15where the engine start control process is executed and the processthereafter ends.

[0109] In step S14, a determination is made as to whether the engine 11is being driven. If the engine 11 is being driven, the operationproceeds to step S16 where the engine stop control process is executedand the operation ends. Otherwise, if the engine is not being driven,the operation proceeds to step S26.

[0110] In step S17, the engine control process is executed and in stepS18, the generator target rotational speed NG* is determined. In stepS19, a determination is made as to whether the absolute value of thegenerator target rotational speed NG* is equal to or higher than thefirst rotational speed Nth1. If the absolute value of the generatortarget rotational speed NG* is equal to or higher than the firstrotational speed Nth1, the operation proceeds to step S20. If theabsolute value of the generator target rotational speed NG* is smallerthan the first rotational speed Nth1, the operation proceeds to stepS21. In step S21, a determination is made as to whether the generatorbrake B is engaged. If the generator brake B is engaged, the operationends. Otherwise, if the generator brake B is not engaged, the operationproceeds to step S22 where the generator brake engage control process isexecuted and the process ends.

[0111] In step S20, a determination is made as to whether the generatorbrake B is released. If the generator brake B is released, the operationproceeds to step S23. If the generator brake B is not released, theoperation proceeds to step S24 where the generator brake release controlprocess is executed and the process ends.

[0112] In step S23, a generator rotational speed control process isexecuted, in step S25, the drive shaft torque TR/OUT is estimated, instep S26, the drive motor target torque TM* is determined and in stepS27, the drive motor control process is executed. The process then ends.

[0113] Next, a subroutine of the sudden acceleration control process instep S 7 of FIG. 7 will be described. FIG. 14 is a drawing illustratingthe subroutine of the sudden acceleration control process according tothe first embodiment of the invention.

[0114] First, the sudden acceleration control processing mechanism readsthe vehicle requirement torque TO* and sets the drive motor maximumtorque TMmax as the drive motor target torque TM*. Then, a generatortarget torque calculation processing mechanism (not shown) of thevehicle control device 51 (FIG. 6) executes a generator target torquecalculation process, in which it calculates a differential torque ΔT ofthe vehicle requirement torque TO* and the drive motor target torqueTM*, and calculates and determines as the generator target torque TG*the amount that the drive motor maximum torque TMmax which is the drivemotor target torque TM* is deficient, and sends the generator targettorque TG* to the generator control device 47.

[0115] Then, the drive motor control processing mechanism executes thedrive motor control process, and controls the torque of the drive motor25 based on the drive motor target torque TM*. Furthermore, a generatortorque control processing mechanism (not shown) of the generator controldevice 47 executes a generator torque control process, and controls thetorque of the generator 16 based on the generator target torque TG*.

[0116] Next, the flow chart of FIG. 14 will be described. In step S7-1,the vehicle requirement torque TO* is read, in step S7-2, the drivemotor maximum torque TMmax as the drive motor target torque TM* is set,in step S7-3, the generator target torque TG* is calculated, in stepS7-4, drive motor control process is executed, and in step S7-5, thegenerator torque control process is executed and the operation returns.

[0117] Next, a subroutine of the drive motor control process in step S27of FIG. 9 and step S7-4 of FIG. 14 will be described. FIG. 15 is adrawing illustrating the subroutine of the drive motor control processaccording to the first embodiment of the invention.

[0118] First, the drive motor control processing mechanism reads thedrive motor target torque TM*. Next, the drive motor rotational speedcalculation processing mechanism reads the drive motor rotor positionθM, and calculates the drive motor rotational speed NM by calculatingthe changing rate ΔθM of the drive motor rotor position θM. Then, thedrive motor control processing mechanism reads the battery voltage VB.In this case, the drive motor rotational speed NM and the batteryvoltage VB constitute an actual measurement value.

[0119] Next, the drive motor control processing mechanism calculates anddetermines a d shaft electric current command value IMd* and a q shaftelectric current command value IMq* based on the drive motor targettorque TM*, the drive motor rotational speed NM, and the battery voltageVB, with reference to the electric current command value map for drivemotor control recorded in the recording equipment of the drive motorcontrol device 49 (FIG. 6). In this case, the d shaft electric currentcommand value IMd* and the q shaft electric current command value IMq*constitute an alternating current command value for the drive motor 25.

[0120] Furthermore, the drive motor control processing mechanism readsthe electric currents IMU and IMV from the electric current sensors 68and 69, and calculates the electric current IMW based on the electriccurrents IMU and IMV:

IMW=IMU−IMV

[0121] In this case, the electric current IMW may also be detected by anelectric current sensor as is the case with the electric currents IMUand IMV.

[0122] Subsequently, an alternating current calculation processingmechanism of the drive motor control processing mechanism executes analternating current calculation process to calculate a d shaft electriccurrent IMd and a q shaft electric current IMq by executing 3 phase/2phase conversion and converting the electric currents IMU, IMV, and IMWinto the d shaft electric current IMd and the q shaft electric currentIMq which are alternating currents. Then, an alternating voltage commandvalue calculation processing mechanism of the drive motor controlprocessing mechanism executes an alternating voltage command valuecalculation process, and calculates voltage command values VMd* and VMq*based on the d shaft electric current IMd and the q shaft electriccurrent IMq, as well as the d shaft electric current command value IMd*and the q shaft electric current command value IMq*. Furthermore, thedrive motor control processing mechanism executes 2 phase/3 phaseconversion to convert the voltage command values VMd* and VMq* into thevoltage command values VMU*, VMV*, and VMW*, calculates pulse-widthmodulation signals SU, SV, and SW based on the voltage command valuesVMU*, VMV*, and VMW*, and outputs the pulse-width modulation signals SU,SV and SW to a drive processing mechanism (not shown) of the drive motorcontrol device 49. The drive processing mechanism executes a driveprocess, and sends the drive signal SG2 to the inverter 29 based on thepulse-width modulation signals SU, SV, and SW. In this case, the voltagecommand values VMd* and VMq* constitute an alternating voltage commandvalue for the drive motor 25.

[0123] Next, the flow chart of FIG. 15 will be described. In this case,since the same process is executed in step S27 and step S7-4, the stepS7-4 will be described. In step S7-4-1, the drive motor target torqueTM* is read, in step S7-4-2, the drive motor rotor position OM is read,in step S7-4-3, the drive motor rotational speed NM is calculated, instep S7-4-4, the battery voltage VB is read, and in step S7-4-5, the dshaft electric current command value IMd* and the q shaft electriccurrent command value IMq*are determined. In step S7-4-6, the electriccurrents IMU and IMV are read, in step S7-4-7, 3 phase/2 phaseconversion is executed, in step S7-4-8, the voltage command values VMd*and VMq* are calculated, in step S7-4-9, 2 phase/3 phase conversion isexecuted, and in step S7-4-10, pulse-width modulation signals SU, SV,and SW are output and the operation returns.

[0124] Next, a subroutine of the generator torque control process instep S7-5 of FIG. 14 will be described. FIG. 16 is a drawingillustrating the subroutine of the generator torque control processaccording to the first embodiment of the invention.

[0125] First, the generator torque control processing mechanism readsthe generator target torque TG*. Then, the generator rotational speedcalculation processing mechanism reads the generator rotor position θGand calculates the generator rotational speed NG based on the generatorrotor position θG. Subsequently, the generator torque control processingmechanism reads the battery voltage VB. Next, the generator torquecontrol processing mechanism, based on the generator target torque TG*,the generator rotational speed NG, and the battery voltage VB, refers tothe electric current command value map for generator control recorded inthe recording equipment of the generator control device 47 (FIG. 6), andcalculates and determines a d shaft electric current command value IGd*and a q shaft electric current command value IGq*. In this case, the dshaft electric current command value IGd* and the q shaft electriccurrent command value IGq* constitute an alternating current commandvalue for the generator 16.

[0126] Furthermore, the generator torque control processing mechanismreads the electric currents IGU and IGV from the electric currentsensors 66 and 67, and calculates an electric current IGW based on theelectric currents IGU and IGV:

IGW=IGU−IGV

[0127] However, the electric current IGW may also be detected by anelectric current sensor as is the case with the electric currents IGUand IGV.

[0128] Subsequently, an alternating current calculation processingmechanism of the generator torque control processing mechanism executesan alternating current calculation process to calculate a d shaftelectric current IGd and a q shaft electric current IGq by executing 3phase/2 phase conversion and converting the electric currents IGU, IGV,and IGW into the d shaft electric current IGd and the q shaft electriccurrent IGq. Then, an alternating voltage command value calculationprocessing mechanism of the generator torque control processingmechanism executes an alternating voltage command value calculationprocess, and calculates voltage command values VGd* and VGq* based onthe d shaft electric current IGd and the q shaft electric current IGq,as well as the d shaft electric current command value IGd* and the qshaft electric current command value IGq*. Furthermore, the generatortorque, control processing mechanism executes 2 phase/3 phase conversionto convert the voltage command values VGd* and VGq* into the voltagecommand values VGU*, VGV*, and VGW*, calculates the pulse-widthmodulation signals SU, SV, and SW based on the voltage command valuesVGU*, VGV*, and VGW*, and outputs the pulse-width modulation signals SU,SV, and SW to a drive processing mechanism (not shown) of the generatorcontrol device 47. The drive processing mechanism executes the driveprocess, and sends the drive signal SG1 to the inverter 28 based on thepulse-width modulation signals SU, SV, and SW. In this case, the voltagecommand values VGd* and VGq* constitute an alternating voltage commandvalue for the generator 16.

[0129] Next, the flow chart of FIG. 16 will be described. In stepS7-5-1, the generator target torque TG* is read, in step S7-5-2, thegenerator rotor position θG is read, in step S7-5-3, the generatorrotational speed NG is calculated, in step S7-5-4, the battery voltageVB is read, and in step S7-5-5, the d shaft electric current commandvalue IGd* and the q shaft electric current command value IGq* aredetermined. In step S7-5-6, the electric currents IGU and IGV are read,in step S7-5-7, 3 phase/2 phase conversion is executed, in step S7-5-8,the voltage command values VGd* and VGq* are calculated, in step S7-5-9,2 phase/3 phase conversion is executed, and in step S7-5-9, pulse-widthmodulation signals SU, SV, and SW are output and the operation ends.

[0130] Next, a subroutine of the engine start control process in stepS15 of FIG. 8 will be described. FIG. 17 is a drawing illustrating thesubroutine of the engine start control process according to the firstembodiment of the invention.

[0131] First, the engine start control processing mechanism reads thethrottle opening θ. If the throttle opening θ is 0 [%], the engine startcontrol processing mechanism reads the vehicle speed V calculated by thevehicle speed calculation processing mechanism, and reads the operationpoint of the engine 11 (FIG. 6) determined in the engine targetoperation state setting process.

[0132] Subsequently, as described earlier, the generator targetrotational speed calculation processing mechanism executes the generatortarget rotational speed calculation process, in which it reads the drivemotor rotor position θM to calculate the ring gear rotational speed NRbased on the drive motor rotor position θM and the gear ratio γR, andreads the engine target rotational speed NE* at the operation point tocalculate and determine the generator target rotational speed NG* basedon the ring gear rotational speed NR and the engine target rotationalspeed NE* using the rotational speed relational expression.

[0133] The engine control device 46 then compares the engine rotationalspeed NE with a preset start rotational speed NEth1, and determineswhether the engine rotational speed NE is higher than the startrotational speed NEth1. If the engine rotational speed NE is higher thanthe start rotational speed NEth1, the engine start control processingmechanism implements fuel injection and ignition of the engine 11.

[0134] Subsequently, the generator rotational speed control processingmechanism executes the generator rotational speed control process basedon the generator target rotational speed NG*, so as to increase thegenerator rotational speed NG and therefore increase the enginerotational speed NE. Thereafter, as similarly carried out in steps S25to step S27, the drive motor control device 49 estimates the drive shafttorque TR/OUT, determines the drive motor target torque TM*, andexecutes the drive motor control process.

[0135] Furthermore, the engine start control processing mechanismadjusts the throttle opening θ so that the engine rotational speed NEbecomes the engine target rotational speed NE*. Next, in order todetermine whether the engine 11 is being driven normally, the enginestart control processing mechanism determines whether the generatortorque TG is less than a motoring torque TEth involved in the start ofthe engine 11, and waits a predetermined time period with the generatortorque TG less than the motoring torque TEth.

[0136] On the other hand, if the engine rotational speed NE is equal toor lower than the start rotational speed NEth1, the generator rotationalspeed control processing mechanism executes the generator rotationalspeed control process based on the generator target rotational speedNG*. Then, as similarly carried out in steps S25 to S27, the drive motorcontrol device 49 estimates the drive shaft torque TR/OUT, determinesthe drive motor target torque TM*, and executes the drive motor controlprocess.

[0137] Next the flow chart of FIG. 17 will be described. In step S15-1,a determination is made as to whether the throttle opening θ is 0 [%].If the throttle opening θ is 0 [%], the operation proceeds to stepS15-3. Otherwise, if the throttle opening is not 0 [%], the operationproceeds to step S15-2 where the throttle opening θ is turned to 0 [%],and the operation returns to step S15-1.

[0138] In step S15-3, the vehicle speed V is read, in step S15-4, theoperation point of the engine 11 is read, and in step S15-5, thegenerator target rotational speed NG* is determined. In step S15-6, adetermination is made as to whether the engine rotational speed NE ishigher than the start rotational speed NEth1. If the engine rotationalspeed NE is higher than the start rotational speed NEth1, the operationproceeds to step S15-11. If the engine rotational speed NE is equal toor lower than the start rotational speed NEth1, the operation proceedsto step S15-7.

[0139] In step S15-7, the generator rotational speed control process isexecuted, in step S15-8, the drive shaft torque TR/OUT is estimated, instep S15-9, the drive motor target torque TM* is determined, and in stepS15-10, the drive motor control process is executed and the operationreturns to step 15-1. In step S15-11, fuel injection and ignition isimplemented, in step S15-12, the generator rotational speed controlprocess is executed, in step S15-13, the drive shaft torque TR/OUT isestimated, in step S15-14, the drive motor target torque TM* isdetermined, in step S15-15, the drive motor control process is executed,and in step S15-16, the throttle opening θ is adjusted.

[0140] In step S15-17, a determination is made as to whether thegenerator torque TG is less than the motoring torque TEth. If thegenerator torque TG is less than the motoring torque TEth, the operationproceeds to step S15-18. If the generator torque TG is equal to orgreater than the motoring torque TEth, the operation returns to stepS15-11. In step S15-18, a predetermined time period elapses, and theoperation returns on the elapse of the predetermined time period.

[0141] Next, a subroutine of the generator rotational speed controlprocess in step S23 of FIG. 9 and steps S15-7 and S15-12 of FIG. 17 willbe described. FIG. 18 is a drawing illustrating the subroutine of thegenerator rotational speed control process according to the firstembodiment of the invention.

[0142] First, the generator rotational speed control processingmechanism reads the generator target rotational speed NG* and thegenerator rotational speed NG. Then, the generator rotational speedcontrol processing mechanism executes PI control based on a differentialrotational speed ΔNG of the generator target rotational speed NG* andthe generator rotational speed NG, and calculates the generator targettorque TG*. In this case, the greater the differential rotational speedΔNG, the greater the generator target torque TG* is increased, with thepositive-negative sign being considered. Subsequently, the generatortorque control processing mechanism executes the generator torquecontrol process of FIG. 16 to control the torque of the generator 16(FIG. 6).

[0143] Next, the flow chart of FIG. 18 will be described. In this case,since the same process is executed in step S23, and steps S15-7 andS15-12, the step S15-7 will be described. In step S15-7-1, the generatortarget rotational speed NG* is read, in step S15-7-2, the generatorrotational speed NG is read, in step S15-7-3, the generator targettorque TG* is calculated, and in step S15-7-4, generator torque controlprocess is executed and the operation returns.

[0144] Next, a subroutine of the engine stop control process in step S16of FIG. 8 will be described. FIG. 19 is a drawing illustrating thesubroutine of the engine stop control process according to the firstembodiment of the invention.

[0145] First, the generator control device 47 (FIG. 6) determineswhether the generator brake B is released. If the generator brake B isengaged and not released, the generator brake release control processingmechanism executes the generator brake release control process andreleases the generator brake B. On the other hand, if the generatorbrake B is released, the engine stop control processing mechanism stopsfuel injection and ignition in the engine 11, and turns the throttleopening θ to 0 [%].

[0146] Subsequently, the engine stop control processing mechanism readsthe ring gear rotational speed NR and determines the generator targetrotational speed NG* based on the ring gear rotational speed NR and theengine target rotational speed NE* (0 [rpm]) using the rotational speedrelational expression. After the generator control device 47 executesthe generator rotational speed control process in FIG. 18, as similarlycarried out in steps S25 to S27, the drive motor control device 49estimates the drive shaft torque TR/OUT, determines the drive motortarget torque TM*, and executes the drive motor control process.

[0147] Next, the generator control device 47 determines whether theengine rotational speed NE is equal to or lower than a stop rotationalspeed NEth2. If the engine rotational speed NE is equal to or lower thanthe stop rotational speed NEth2, the generator control device 47 stopsthe switching for the generator 16 to shut down the generator 16.

[0148] Next, the flow chart of FIG. 19 will be described. In step S16-1,a determination is made as to whether the generator brake B is released.If the generator brake B is released, the operation proceeds to stepS16-3. If the generator brake B is not released, the operation proceedsto step S16-2 where generator brake release control process is executed.In step S16-3, fuel injection and ignition is stopped, in step S16-4,the throttle opening θ is turned to 0 [%], in step S16-5, the generatortarget rotational speed NG* is determined, in step S16-6, the generatorrotational speed control process is executed, in step S16-7, the driveshaft torque TR/OUT is estimated, in step S16-8, the drive motor targettorque TM* is determined, and in step S16-9, drive motor control processis executed, in step S16-10, a determination is made as to whether theengine rotational speed NE is equal to or lower than the stop rotationalspeed NEth2. If the engine rotational speed NE is equal to or lower thanthe stop rotational speed NEth2, the operation proceeds to step S16-11.If the engine rotational speed NE is greater than the stop rotationalspeed NEth2, the operation returns to step S16-5. In step S16-11, theswitching for the generator 16 is stopped and the operation returns.

[0149] Next, a subroutine of the generator brake engage control processin step S22 of FIG. 9 will be explained. FIG. 20 is a drawingillustrating the subroutine of the generator brake engage controlprocess according to the first embodiment of the invention.

[0150] First, the generator brake engage control processing mechanismchanges the generator brake requirement for requiring the engagement ofthe generator brake B (FIG. 6) from OFF to ON, and sets the generatortarget rotational speed NG* to 0 [rpm]. After the generator controldevice 47 executes the generator rotational speed control process inFIG. 18, as similarly carried out in steps S25 to S27, the drive motorcontrol device 49 estimates the drive shaft torque TR/OUT, determinesthe drive motor target torque TM*, and executes the drive motor controlprocess.

[0151] Next, the generator brake engage control processing mechanismdetermines whether the absolute value of the generator rotational speedNG is smaller than a predetermined second rotational speed Nth2 (forexample, 100 [rpm]), and engages the generator brake B if the absolutevalue of the generator rotational speed NG is smaller than the secondrotational speed Nth2. Subsequently, as similarly carried out in stepsS25 to S27, the drive motor control device 49 estimates the drive shafttorque TR/OUT, determines the drive motor target torque TM*, andexecutes the drive motor control process.

[0152] Then, after a predetermined time period has passed with thegenerator brake B engaged, the generator brake engage control processingmechanism stops the switching for the generator 16 to shut down thegenerator 16.

[0153] Next, the flow chart of FIG. 20 will be described. In step S22-1,the generator target rotational speed NG* is set to 0 [rpm], in stepS22-2, the generator rotational speed control process is executed, instep S22-3, the drive shaft torque TR/OUT is estimated, in step S22-4,the drive motor target torque TM* is determined, and in step S22-5,drive motor control process is executed. In step S22-6, a determinationis made as to whether the absolute value of the generator rotationalspeed NG is smaller than the second rotational speed Nth2. If theabsolute value of the generator rotational speed NG is smaller than thesecond rotational speed Nth2, the operation proceeds to step S22-7. Ifthe absolute value of the generator rotational speed NG is equal to orgreater than the second rotational speed Nth2, the operation returns tostep S22-2.

[0154] In step S22-7, the generator brake B is engaged, in step S22-8,the drive shaft torque TR/OUT is estimated, in step S22-9, the drivemotor target torque TM* is determined, and in step S22-10, the drivemotor control process is executed. In step S22-11, a determination ismade as to whether a predetermined time period has passed. If thepredetermined time period has passed, the operation proceeds to stepS22-12 where the switching for the generator 16 is stopped and theoperation returns. Otherwise, the operation returns to step S22-7.

[0155] Next, a subroutine of the generator brake release control processin step S24 of FIG. 9 will be described. FIG. 21 is a drawingillustrating the subroutine of the generator brake release controlprocess according to the first embodiment of the invention.

[0156] In the generator brake engage control process, while thegenerator brake B (FIG. 6) is engaged, a predetermined engine torque TEis applied to the rotor 21 of the generator 16 as a reaction force.Therefore, when the generator brake B is simply released, the enginetorque TE is transmitted to the rotor 21, causing a great change in thegenerator torque TG and the engine torque TE, thereby generating ashock.

[0157] Therefore, in the engine control device 46, the engine torque TEthat is transmitted to the rotor 21 is estimated or calculated, and thegenerator brake release control processing mechanism reads the torqueequivalent to the estimated or calculated engine torque TE, i.e., enginetorque equivalent, and sets the engine torque equivalent as thegenerator target torque TG*. Then, after the generator torque controlprocessing mechanism executes the generator torque control process inFIG. 16, as similarly carried out in steps S25 to S27, the drive motorcontrol device 49 estimates the drive shaft torque TR/OUT, determinesthe drive motor target torque TM*, and executes the drive motor controlprocess.

[0158] When a predetermined time period has passed after the start ofthe generator torque control process, the generator brake releasecontrol processing mechanism releases the generator brake B and sets thegenerator target rotational speed NG* to 0 [rpm]. Then, the generatorrotational speed control mechanism executes the generator rotationalspeed control process in FIG. 18. Subsequently, as similarly carried outin steps S25 to S27, the drive motor control device 49 estimates thedrive shaft torque TR/OUT, determines the drive motor target torque TM*,and executes the drive motor control process. In this case, the enginetorque equivalent is estimated or calculated by learning the torqueratio of the generator torque TG to the engine torque TE.

[0159] Next, the flow chart of FIG. 21 will be described. In step S24-1,the engine torque equivalent is set as the generator target torque TG*,in step S24-2, the generator torque control process is executed, in stepS24-3, the drive shaft torque TR/OUT is estimated, in step S24-4, thedrive motor target torque TM* is determined, and in step S24-5, drivemotor control process is executed.

[0160] In step S24-6, a determination is made as to whether apredetermined time period has passed. If the predetermined time periodhas passed, the operation proceeds to step S24-7. If not, the operationreturns to step S24-2. In step S24-7, the generator brake B is released,in step S24-8, the generator target rotational speed NG* is set to 0[rpm], in step S24-9, the generator rotational speed control process isexecuted, in step S24-10, the drive shaft torque TR/OUT is estimated, instep S24-11, the drive motor target torque TM* is determined, and instep S24-12, drive motor control process is executed and the processreturns.

[0161] Meanwhile, in the engine target operation state setting process,as shown in FIG. 12, the points Al to A 3, and Am at which the linesPO1, P02, . . . which indicate the vehicle requirement output POintersect the optimum fuel consumption curve L where the engine 11reaches maximum efficiency, at each accelerator pedal position AP1 toAP6, are determined as operation points of the engine 11 which areengine target operation states, and engine torque TE1 to TE3 and TEm atthe operation points are determined as the engine target torque TE*.

[0162] Therefore, when the vehicle requirement output PO becomes smalleras the vehicle requirement torque TO* becomes smaller, the engine targettorque TE* is also reduced. If the vehicle requirement output PO becomessmaller than a predetermined value, however, it is not possible toaccordingly reduce the engine target torque TE*. Thus, the excessive ordeficient amount of torque of the engine torque TE with respect to thevehicle requirement torque TO* is compensated for using the drive motor25.

[0163] On the other hand, if the engine torque TE is greater than thevehicle requirement torque TO*, a regenerative processing mechanism (notshown) of the vehicle control device 51 executes a regenerative process,calculates the amount that the engine torque TE has exceeded the vehiclerequirement torque TO*, and sends the calculated excessive amount to thedrive motor control device 49 as regenerative target torque. Then, thedrive motor control device 49 drives the drive motor 25 based on theregenerative target torque to absorb as regenerative torque the drivemotor torque TM that corresponds to the excessive amount of torque, andgenerates electrical energy to charge the battery 43.

[0164] To accomplish this, a regenerative control processing mechanism(not shown) of the drive motor control device 49 executes a regenerativecontrol process, sends the drive signal SG2 to the inverter 29 anddrives the inverter 29. As a result, the alternating current generatedin the drive motor 25 is converted to direct current in the inverter 29.Then, the direct current is sent to the battery 43 and regenerativetorque is generated in the drive motor 25.

[0165] Meanwhile, when the hybrid vehicle is driven with the amount ofengine torque TE in excess of the vehicle requirement torque TO*absorbed by the drive motor 25 as regenerative torque, electrical energyis generated in the drive motor 25. However, when, for example,overheating of the drive motor 25 occurs along with the generation ofelectrical energy, then it becomes necessary to limit the regenerativetorque.

[0166] Therefore, the index determination processing mechanism 91(FIG. 1) of the vehicle control device 51 executes an indexdetermination process, reads the temperature tmM of the coil 42 detectedby the drive motor temperature sensor 65 and determines whether thetemperature tmM has exceeded a threshold value tmMth, i.e., whether thetemperature tmM has become higher than the threshold value tmMth. If thetemperature tmM has become higher than the threshold value tmMth, thetorque limit processing mechanism 92 of the vehicle control device 51executes a torque control process to limit the regenerative torque.Therefore, the torque limit processing mechanism 92 limits and reducesthe drive motor target torque TM* during regeneration. In this case, thetemperature tmM of the coil 42 indicates the torque limit index that isthe index for limiting regenerative torque when regenerative torque isabsorbed by the drive motor 25. Furthermore, a drive motor drive portionis constituted by the drive motor 25.

[0167]FIG. 22 is a drawing illustrating a limiting method for drivemotor target torque according to the first embodiment of the invention.In the drawing, the x-axis is the temperature tmM and the y-axis is thelimit ratio ρ. As shown in the drawing, when the temperature tmM isequal to or lower than the threshold value tmMth, the limit ratio ρ is 1and the drive motor target torque TM* during regeneration is notlimited. On the other hand, when the temperature tmM becomes higher thanthe threshold value tmMth, the limit ratio ρ decreases as thetemperature tmM increases, and thus the drive motor target torque TM* islimited and becomes ρ· TM*.

[0168] In this embodiment, when the temperature tmM becomes higher thanthe threshold value tmMth, the limit value ρ is gradually reduced asexpressed by a linear function, but it can also be reduced using anotherfunction. Furthermore, in addition to the case where the drive motor 25has overheated and a temperature of the drive motor 25 (FIG. 6), forexample, the temperature tmM of the coil 42, has become higher than thethreshold value tmMth, the case where a temperature of the inverter 29,a temperature of the cooling oil for cooling the drive motor 25, or thelike, has become higher than a threshold value or the case where anabnormal state has occurred in the hybrid vehicle drive device may alsobe considered as a state that requires limiting of the regenerativetorque. In this case, a temperature sensor such as an invertertemperature sensor for detecting a temperature of the inverter 29 or acooling oil temperature sensor for detecting a temperature of thecooling oil that cools the drive motor 25 is provided as the torquelimit index detection portion in place of the drive motor temperaturesensor 65. When the temperature of the inverter 29, the temperature ofthe cooling oil for cooling the drive motor 25, or the like, has becomehigher than the respective threshold value or an abnormal state hasoccurred in the hybrid vehicle drive device, the sending of the drivesignal SG2 to the inverter 29 is stopped. The drive of the inverter 29is therefore stopped, thus limiting the regenerative torque in the drivemotor 25.

[0169] In this case, the drive motor drive portion comprises the drivemotor 25, the inverter 29 and a cooling system of the drive motor 25,and the drive motor drive portion temperature that indicates the torquelimit index comprises the temperature of the drive motor 25, thetemperature of the inverter 29, the temperature of the cooling oil andthe like.

[0170] Furthermore, a state where a drive motor inverter voltage VM, adrive motor inverter current IM, an electrical output or the like,generated on the input port side of the inverter 29 in accordance withregeneration is decreased equal to or lower than a threshold may also beconsidered as the state that requires limiting of the regenerativetorque. In this case, a drive motor inverter voltage sensor 76 fordetecting the drive motor inverter voltage VM, a drive motor invertercurrent sensor 78 for detecting the drive motor inverter current IM, andan electrical output calculation processing mechanism for detecting theelectrical output constitutes the torque limit index detection portion,so that when the drive motor inverter voltage VM, the drive motorinverter current IM, and the electrical output has become higher thanthe threshold value, the sending of the drive signal SG2 to the inverter29 is stopped. The drive of the inverter 29 is therefore stopped, thuslimiting the regenerative torque in the drive motor 25. Furthermore, anelectrical output calculation processing mechanism (not shown) of thedrive motor control device 49 may also execute an electrical outputcalculation process to calculate an electrical output based on thevoltage and the current, so that when the calculated electrical outputhas exceeded a threshold value, the sending of the drive signal SG2 tothe inverter 29 is stopped. The drive of the inverter 29 is thereforestopped, thus limiting the regenerative torque in the drive motor 25.

[0171] In this case, the drive motor drive portion comprises theinverter 29, and the electrical variable that indicates the torque limitindex comprises the drive motor inverter voltage VM, the drive motorinverter current IM, and the electrical output. Furthermore, the torquelimit index detection portion comprises the drive motor inverter voltagesensor 76, the drive inverter current sensor 78 and the electricaloutput calculation mechanism.

[0172] Meanwhile, when the regenerative torque is limited in the torquelimit process executed by the torque limit processing mechanism 92 (FIG.1), and therefore the drive motor target torque TM* is limited, theamount of engine torque TE in excess of the vehicle requirement torqueTO* is absorbed by the drive motor 25 as regenerative torque. If theregenerative torque is limited, an engine torque TE greater than thevehicle requirement torque TO* is transmitted to the drive wheel 37,thereby imparting an unpleasant sensation to the driver.

[0173] Therefore, the engine control processing mechanism limits theengine torque TE by only the amount that the regenerative torque islimited. Specifically, the engine control processing mechanism limitsthe engine torque TE so that the sum of the limited regenerative torqueand the engine torque TE satisfies the vehicle requirement torque TO*,and therefore limiting the engine target torque TE*.

[0174] A subroutine of the engine control process in step S17 of FIG. 8will hereafter be explained. FIG. 23 is a drawing illustrating thesubroutine of the engine control process according to the firstembodiment of the invention, FIG. 24 is a first time chart illustratingan operation of the engine control process according to the firstembodiment of the invention, and FIG. 25 is a second time chartillustrating the operation of the engine control process according tothe first embodiment of the invention.

[0175] First, a torque limit determination processing mechanism (notshown) of the engine control processing mechanism executes a torquelimit determination process, and determines whether the regenerativetorque is limited according to whether the drive motor target torque TM*is limited. If the drive motor target torque TM* is limited, and theregenerative torque is limited, the engine torque adjustment processingmechanism 93 (FIG. 1) of the engine control processing mechanismexecutes an engine torque adjustment process and adjusts the enginetorque TE. To accomplish this, the engine torque adjustment processingmechanism 93 calculates the difference between the drive motor targettorque TM* before limiting and the drive motor target torque ρ· TM*after limiting, i.e., the target torque difference ΔTM*:

ΔTM*=TM*·ρTM*

[0176] Next, the engine torque adjustment processing mechanism 93calculates an engine torque equivalent ΔTE* of the target torquedifference ΔTM* in order to adjust the engine target torque TE* by onlythe limited amount of the drive motor target torque TM*, i.e. only theamount of the target torque difference ΔTM*:

ΔTE*=γem·ΔTM*

[0177] In this case, γem is a gear ratio from the engine 11 (FIG. 2) tothe drive motor 25. When a gear ratio from the engine 11 to the drivewheel 37 (the same as the gear ratio from the engine 11 to the pinion(not shown) of the differential device 36) is, γew and a gear ratio fromthe drive motor 25 to the drive wheel 37 is γ mw, the gear ratio γem iscalculated as follows:

γem=γew/γmw

[0178] Next, the engine torque adjustment processing mechanism 93adjusts the engine target torque TE* by only the amount of the enginetorque equivalent ΔTE*. If the engine target torque after adjustment isrepresented as TE{acute over (η)}*, then the engine target torqueTE{acute over (η)}* can be calculated as follows:

TE{acute over (η)}*=TE*+ΔTE*

[0179] In this case, the drive motor target torque TM* and ρ· TM* arevalues during regeneration and assume negative values. Furthermore,because TM*<ρ· TM*, the target torque difference ΔTM* also assumes anegative value and the engine torque equivalent ΔTE* also assumes anegative value. In this way, if the engine target torque TE* isadjusted, the engine control processing mechanism sets the limitedengine target torque TE{acute over (η)}* as the engine target torque TE*and drives the engine 11.

[0180] Therefore, for example, during regeneration of the drive motor25, if the temperature tmM in timing t1 becomes higher than thethreshold value tmMth, then the regenerative torque is limited from thetiming t1 to the timing t2, and the drive motor target torque TM* islimited and increased (the absolute value |TM*| is reduced) by only theamount of the target torque difference ΔTM*. Therefore, as shown in FIG.24, the drive motor torque TM (regenerative torque) during regenerationis gradually increased (the absolute value |TM*| is reduced) from thetiming t1 to the timing t2.

[0181] Then, as the drive motor target torque TM* is limited, the enginetarget torque TE* is limited and reduced by only the amount of theengine torque equivalent ΔTE*. Therefore, as shown in FIG. 24, theengine torque TE during regeneration is gradually reduced from thetiming t1 to the timing t2.

[0182] As a result, a vehicle output torque TO, obtained by addingtogether the drive motor torque TM and the engine torque TE, assumes aconstant value without being varied from the timing t1 to the timing t2.In this way, when a torque limit index has exceeded a threshold valueand it has become necessary to limit the regenerative torque of thedrive motor 25, the engine torque TE is limited and reduced by thatamount only. Therefore, an engine torque TE greater than the vehiclerequirement torque TO* is not transmitted to the drive wheel 37, thus anunpleasant sensation is not imparted to the driver.

[0183] Note that the broken lines in FIG. 24 indicate the vehicle outputtorque TO when the engine target torque inverter voltage has not beenadjusted when the regenerative torque is limited. Meanwhile, if thevehicle requirement output PO becomes larger as the vehicle requirementtorque TO* becomes larger, the engine target torque TE* is also made toincrease. If the vehicle requirement torque TO* becomes greater than apredetermined value, however, it is not possible to accordingly increasethe engine target torque TE*. Thus, a powering control processingmechanism (not shown) of the vehicle control device 51 (FIG. 6) executesa powering control process, calculates the deficient amount by which theengine target torque TE* is deficient with respect to the vehiclerequirement torque TO*, and sends the calculated deficient amount to thedrive motor control device 49 as powering target torque. Then, the drivemotor control device 49 drives the drive motor 25 based on the poweringtarget torque and supplements as powering torque the drive motor torqueTM corresponding to the deficient amount.

[0184] Meanwhile, if the temperature tmM becomes greater than thethreshold value tmMth for some reason during powering of the drive motor25, the index determination processing mechanism 91 reads thetemperature tmM of the coil 42 detected by the drive motor temperaturesensor 65 which is the torque limit index detection portion, anddetermines whether the temperature tmM has exceeded the threshold valuetmMth, i.e., whether the temperature tmM has become higher than thethreshold value tmMth. If the temperature tmM has become higher than thethreshold value tmMth, the torque limit processing mechanism 92 executesa torque control process and limits and reduces the powering torque.

[0185] To accomplish this, the torque limit processing mechanism 92limits the drive motor target torque TM* during powering (positivevalue) and reduces it by only the amount of the target torque differenceΔTM* (the absolute value |TM*| is also reduced). As a result, as shownin FIG. 25, the drive motor torque TM (powering torque) is graduallyreduced from timing t11 to timing t12 (the absolute value |TM*| is alsoreduced).

[0186] In this case, according to this, the vehicle output torque TO isreduced, as shown by the broken lines. If an engine torque TE smallerthan the vehicle requirement torque TO* is transmitted to the drivewheel 37, then an unpleasant sensation is imparted to the driver.

[0187] Therefore, as the drive motor target torque TM* is limited sothat the sum of the limited drive motor target torque TM* and the enginetarget torque TE* satisfies the vehicle requirement torque TO*, theengine torque adjustment processing mechanism 93 adjusts the enginetarget torque TE* from the timing t11 to the timing t12, increasing itby only the amount of the engine torque equivalent ΔTE* of the targettorque difference ΔTM*. Accordingly, the engine torque TE duringpowering is gradually increased from the timing t1 to the timing t2.

[0188] As a result, the vehicle output torque TO obtained by adding thedrive motor torque TM and the engine torque TE assumes a constant valuewithout being varied from the timing t11 to the timing t12. Note thatthe broken lines indicate the vehicle output torque TO when the enginetarget torque TE* has not been adjusted when the powering torque islimited.

[0189] Note that the temperature tmM of the coil 42 indicates the torquelimit index for limiting the powering torque when the powering torque isgenerated by the drive motor 25. Furthermore, the drive motor driveportion is constituted by the drive motor 25.

[0190] Next, the flowchart of FIG. 23 will be described. In step S17-1,a determination is made as to whether the drive motor target torque TM*is limited. If the drive motor target torque TM* is limited, theoperation proceeds to step S17-2. If not limited, the operation proceedsto step S17-5. In step S17-2, the target torque difference ΔTM* iscalculated, in step S17-3, the engine torque equivalent ΔTE* iscalculated in step SI 7-4, the engine target torque TE* is adjusted andin step S17-5, the engine 11 is driven with the engine target torque TE*and the operation returns.

[0191] Meanwhile, in the hybrid vehicle described above, when a driverselects a reverse range by manipulating a shift lever in order to movethe hybrid vehicle backward, the drive motor 25 is driven in a reversedirection, so that the drive motor torque TM and the drive motorrotational speed NM assume negative values and the ring gear R isrotated in the reverse direction.

[0192] Subsequently, the vehicle control device 51 reads a shiftposition SP detected by the shift position sensor 53 and determineswhether the reverse range is selected based upon the shift position SP.If the reverse range is selected, the vehicle control device 51calculates the drive motor target torque TM* which is a negative value,and transmits it to the drive motor control device 49. Upon receivingthe drive motor target torque TM*, the drive motor control device 49reversely drives the drive motor 25 based upon the drive motor targettorque TM*, thereby rotating the drive wheel 37 in the reversedirection. Thus, the hybrid vehicle can be driven backward.

[0193] As described above, if it becomes necessary to limit the drivemotor torque TM for some reason when a driver starts to move the hybridvehicle backward while running the engine 11, it is difficult to drivethe hybrid vehicle backward unless the drive motor torque TM in thereverse direction is generated such that it is sufficient to overpowerthe engine TE. This imparts an unpleasant sensation to the driver.

[0194] To overcome such a problem, a hybrid vehicle drive control deviceaccording to a second embodiment of the invention, which will hereafterbe described, has been developed in order to reliably drive the hybridvehicle backward by adjusting engine torque TE if it becomes necessaryto limit drive motor torque TM when the hybrid vehicle is started tomove backward. The structures and the like of this embodiment that aresubstantially the same as those of the first embodiment are representedby like reference numerals in the drawings, and will not be explainedagain.

[0195] In this case, the index determination processing mechanism 91(FIG. 1) of the vehicle control device 51 (FIG. 6) executes an indexdetermination process, reads the temperature tmM of the coil 42 detectedby the drive motor temperature sensor 65 and determines whether thetemperature tmM has exceeded a threshold value tmMth, i.e., whether thetemperature tmM has become higher than the threshold value tmMth. If thetemperature tmM has become higher than the threshold value tmMth, thetorque limit processing mechanism 92 of the vehicle control device 51executes a torque control process to limit the drive motor torque TM.Therefore, the torque limit processing mechanism 92 limits and reducesthe drive motor torque TM* during backward movement.

[0196] In this case, the temperature tmM indicates the torque limitindex that is the index for limiting drive motor torque TM when thedrive motor torque TM is limited by the drive motor 25. Furthermore, adrive motor drive portion comprises the drive motor 25. As shown in FIG.22, when the temperature tmM is equal to or lower than the thresholdvalue tmMth, the limit ratio ρ is 1 and the drive motor target torqueTM* during regeneration is not limited. On the other hand, when thetemperature tmM becomes higher than the threshold value tmMth, the limitratio ρ decreases as the temperature tmM increases, and thus the drivemotor target torque TM* is limited and becomes ρ· TM*.

[0197] Furthermore, as in the case in which limiting of the generativetorque is required, in addition to the case where the drive motor 25 hasoverheated and a temperature of the drive motor 25, for example, thetemperature tmM of the coil 42, has become higher than the thresholdvalue tmMth, a case such as where a temperature of the inverter 29, atemperature of the cooling oil for cooling the drive motor 25, or thelike, has become higher than a threshold value or a case in which anabnormal state has occurred in the hybrid vehicle drive device may alsobe considered as a state that requires limiting of the drive motortorque TM. In this case, a temperature sensor such as an invertertemperature sensor for detecting a temperature of the inverter 29 or acooling oil temperature sensor for detecting a temperature of thecooling oil that cools the drive motor 25 is provided as the torquelimit index detection portion in place of the drive motor temperaturesensor 65. When the temperature of the inverter 29, the temperature ofthe cooling oil for cooling the drive motor 25, or the like, has becomehigher than the respective threshold value or an abnormal state hasoccurred in the hybrid vehicle drive device, the sending of the drivesignal SG2 to the inverter 29 is stopped. The drive of the inverter 29is therefore stopped, thus limiting the regenerative torque in the drivemotor 25.

[0198] In this case, the drive motor drive portion comprises the drivemotor 25, the inverter 29 and a cooling system of the drive motor 25,and the drive motor drive portion temperature that indicates the torquelimit index comprises the temperature of the drive motor 25, thetemperature of the inverter 29, the temperature of the cooling oil andthe like.

[0199] Furthermore, a state where a voltage, a current, an electricaloutput or the like, generated on the input port side of the inverter 29in accordance with regeneration is decreased equal to or lower than athreshold may also be considered as the state that requires limiting ofthe regenerative torque. In this case, the torque limit index detectionportion comprises a voltage sensor, a current sensor, or the like fordetecting a voltage, current, or the like, generated on the input sideof the inverter 29 constitutes. When the voltage, the current, or thelike on the input side of the inverter 29 has become higher than therespective threshold value, the torque limit index detection portionstops the sending of the drive-signal SG2 to the inverter 29, the driveof the inverter 29, and thus limits the regenerative torque in the drivemotor 25. Furthermore, an electrical output calculation processingmechanism (not shown) of the drive motor control device 49 may alsoexecute an electrical output calculation process to calculate anelectrical output based on the voltage and the current, so that when thecalculated electrical output has exceeded a threshold value, the sendingof the drive signal SG2 to the inverter 29 is stopped. The drive of theinverter 29 is therefore stopped, thus limiting the drive motor torqueTM in the drive motor 25.

[0200] In this case, the drive motor drive portion comprises theinverter 29, and the electrical variable that indicates the torque limitindex comprises the voltage, the current, and the electrical output.Furthermore, the torque limit index detection portion comprises thevoltage sensor, the current sensor, and the electrical outputcalculation mechanism.

[0201] Meanwhile, in the hybrid vehicle as described above, when thebattery remaining charge SOC becomes less, the battery charge/dischargerequirement output PB becomes greater. The vehicle requirement output POalso becomes greater and a driving point for the engine 11 whichcorresponds to the vehicle requirement output PO is determined.Consequently, the engine 11 is driven at the driving point and power isgenerated by the generator 16. In addition, even if a load applied onthe battery 43 becomes greater due to the running of an auxiliarydevice, such as an air-conditioner, which consumes much power, theengine 11 is driven and power is generated by the generator 16.

[0202] As mentioned above, if it becomes necessary to limit the drivemotor torque TM for some reason when a driver starts to move the hybridvehicle backward while running the engine 11, it is difficult to drivethe hybrid vehicle backward unless the drive motor torque TM in thereverse direction is generated such that it is sufficient to overpowerthe engine torque TE. This imparts an uncomfortable sensation to thedriver.

[0203] In order to prevent such a problem, the engine control processingmechanism limits the engine torque TE by only an amount that the drivemotor torque TM is limited. Specifically, it limits the engine torque TEso that the sum of the limited drive motor torque TM and the enginetorque TE satisfies the vehicle requirement torque TO*, thereforelimiting the engine target torque TE*.

[0204] Next, a subroutine of the engine control process in step S17 ofFIG. 8 will be described. FIG. 26 is a drawing illustrating thesubroutine of the engine control process according to the secondembodiment of the invention and FIG. 27 is a time chart illustrating anoperation of the engine control process according to the secondembodiment of the invention.

[0205] First, a range determination processing mechanism (not shown) ofthe engine control processing mechanism executes a range determinationprocess in order to read the shift position SP and determine whether areverse range is selected based upon the shift position SP. If thereverse range is selected, the torque limit determination processingmechanism (not shown) of the engine control processing mechanismperforms a torque limit determination process in order to determinewhether the drive motor torque TM is limited according to whether drivemotor target torque TM* is limited. If the drive motor target torque TM*is limited and the drive motor torque TM is limited, the engine torqueadjustment processing mechanism 93 (FIG. 1) of the engine controlprocessing mechanism executes, as in the case of the first embodiment,an engine torque adjustment process and adjusts the engine torque TE. Toaccomplish this, the engine torque adjustment processing mechanism 93calculates the difference between the drive motor target torque TM*before limiting and the drive motor target torque ρ· TM* after limiting,i.e., the target torque difference ΔTM*:

ΔTM*=TM*−ρ·TM*

[0206] Next, the engine torque adjustment processing mechanism 93calculates the engine torque equivalent ΔTE* of the target torquedifference ΔTM* in order to adjust the engine target torque TE* by onlythe amount of the target torque difference ΔTM*. Subsequently, theengine torque adjustment processing mechanism 93 adjusts the enginetarget torque TE* by only an amount of the engine torque equivalentΔTE*. If the engine target torque after adjustment is represented asTE{acute over (η)}*, then the engine target torque TE{acute over (η)}*can be calculated as follows:

TE{acute over (η)}*=TE*+ΔTE*

[0207] In this case, the drive motor target torque TM* and ρ· TM* arevalues during powering for driving the hybrid vehicle backward, andassume negative values. Furthermore, because TM*<ρ· TM*, the targettorque difference ΔTM* also assumes a negative value and the enginetorque equivalent ΔTE* also assumes a negative value. In this way, ifthe engine target torque TE* is adjusted, the engine control processingmechanism sets the limited engine target torque TE{acute over (η)}* asthe engine target torque TE* and drives the engine 11 (FIG. 6).

[0208] Therefore, for example, during powering of the drive motor 25, ifthe temperature tmM in timing t 21 becomes higher than the thresholdvalue tmMth, then the drive motor torque TM is limited from the timingt21 to timing t22, and the drive motor target torque TM* is limited andincreased (the absolute value |TM*| is reduced) by only the amount ofthe target torque difference ΔTM*. Therefore, as shown in FIG. 27, thedrive motor torque TM (powering torque) during powering for driving thehybrid vehicle backward is gradually increased (the absolute value |TM*|is reduced) from the timing t21 to the timing t22.

[0209] Then, as the drive motor target torque TM* is limited, the enginetarget torque TE* is limited and reduced by only the amount of theengine torque equivalent ΔTE*. Therefore, as shown in FIG. 27, theengine torque TE during regeneration is gradually reduced from thetiming t21 to the timing t22.

[0210] As a result, a vehicle output torque TO, obtained by addingtogether the drive motor torque TM and the engine torque TE, assumes aconstant value without being varied from the timing t21 to the timingt22.

[0211] In this way, when a torque limit index has exceeded a thresholdvalue and it has become necessary to limit the drive motor torque TM ofthe drive motor 25, the engine torque TE is limited and reduced by onlythat amount. Therefore, the drive motor torque TM in the reversedirection is generated such that it is sufficient to overpower theengine torque TE, and this makes it easy to drive the hybrid vehiclebackward. Accordingly, a driver does not have an unpleasant sensation.

[0212] Note that the broken lines in FIG. 27 indicate the vehicle outputtorque TO when the engine target torque TE* has not been adjusted whenthe drive motor torque TM is limited

[0213] Next, the flowchart of FIG. 26 will be described. In step S17-11,a determination is made as to whether the reverse range is selected. Ifthe reverse range is selected, the operation proceeds to step S17-12. Ifthe reverse range is not selected, the operation proceeds to stepS17-16. In step S17-12, a determination is made as to whether the drivemotor target torque TM* is limited. If the drive motor target torque TM*is limited, the operation proceeds to step S17-13. If not, the operationproceeds to step S17-16. In step S17-13, the target torque differenceΔTM* is calculated, in step S17-14, the engine torque equivalent ΔTE* iscalculated, in step S17-15, the engine target torque TE* is adjusted,and in step S17-16, the engine 11 is driven with the engine targettorque TE*, and the operation returns.

[0214] A hybrid vehicle drive control device according to a thirdembodiment of the invention will hereafter be described. The hybridvehicle drive control device of the third embodiment reliably moves thevehicle backward when a reverse range is selected in a situation wherethe drive motor 25 cannot output the drive motor torque TM sufficient tooverpower the engine torque TE even though the engine torque TE islimited due to, for example, abnormal overheating of the drive motor 25or an insufficient amount of charges in the battery 43 caused tomalfunction.

[0215]FIG. 28 is a drawing illustrating the subroutine of the enginecontrol process according to the third embodiment of the invention. Inthis case, the torque limit determination processing mechanism (notshown) of the engine control processing mechanism performs the torquelimit determination process in order to determine whether the drivemotor torque TM is limited according to whether the drive motor targettorque TM* is limited. If the drive motor target torque TM* is limitedand the drive motor torque TM is limited, the range determinationprocessing mechanism (not shown) of the engine control processingmechanism executes the range determination process in order to read theshift position SP and determines whether the reverse range is selectedbased upon the shift position SP. If the reverse range is selected, theengine stop control processing mechanism (not shown) of the enginecontrol processing mechanism executes the engine stop control process inorder to stop fuel injection and ignition in the engine 11 (FIG. 6) andturn the throttle opening θ to 0 [%], thereby stopping the engine 11.

[0216] If the reverse range is not selected, the engine torqueadjustment processing mechanism 93 (FIG. 1) of the engine controlprocessing mechanism performs the engine torque adjustment process. Inthis way, if the reverse range is selected when the torque limit indexhas exceeded the threshold and it has become necessary to limit thedrive motor torque TM of the drive motor 25, the engine 11 is stoppedand the engine torque TE becomes zero. Accordingly, the drive motortorque TM in the reverse direction can be reliably generated.

[0217] Accordingly, this facilitates backward moving of the hybridvehicle and prevents an unpleasant sensation from being imparted to adriver. In the present embodiment, when the reverse range is selected,the engine stop control processing mechanism executes the engine stopcontrol process in order that the fuel injection and ignition of theengine 11 are stopped and the throttle opening θ is turned to 0 [%],thereby stopping the engine 11. However, the engine control processingmechanism may bring the engine 11 into an idling state. In this case,the engine control processing mechanism brings about the idling state bysetting the engine target torque TE* to zero.

[0218] Next, the flowchart of FIG. 28 will be described. In step S17-21,a determination is made as to whether the drive motor target torque TM*is limited. If the drive motor target torque TM* is limited, theoperation proceeds to step S17-22. If not limited, the operationproceeds to step S17-22. In step 17-22, a determination is made as towhether the reverse range is selected. If the reverse range is selected,the operation proceeds to step S17-23 where the engine is stopped andthe operation returns. If not selected, the operation proceeds to stepS17-24.

[0219] In step S17-24, the target torque difference ΔTM* is calculated,in step S17-25, the engine torque equivalent ΔTE* is calculated, in stepS17-26, the engine target torque TE* is adjusted, and in step S17-27,the engine 11 is driven with the engine target torque TE*, and theoperation returns.

[0220] In the third embodiment, the case where, when the reverse rangeis selected for example, the engine 11 is stopped or brought into anidling state has been discussed. However, this embodiment may bring theengine 11 into a stopped state or an idling state while selecting aforward range.

[0221] The invention is not limited to the aforementioned embodiments,and various modifications based on the purpose of the invention arepossible, which are regarded as within the scope of the invention.

1. A hybrid vehicle control device, comprising: a drive motor thatcompensates for an excessive or a deficient amount of engine torque withrespect to a vehicle requirement torque; and a controller that: detectsa torque limit index, which is an index that limits a drive motortorque; determines whether the torque limit index has exceeded athreshold value; limits the drive motor torque when the torque limitindex has exceeded the threshold value; and adjusts the engine torque,in accordance with a limiting of the drive motor torque.
 2. The hybridvehicle control device according to claim 1, wherein the torque limitindex is a temperature of a drive motor drive portion.
 3. The hybridvehicle drive control device according to claim 1, wherein the torquelimit index is an electrical variable of a motor drive portion.
 4. Thehybrid vehicle control device according to claim 1, wherein thecontroller limits a regenerative torque during regeneration of the drivemotor, the regeneration of the drive motor for absorbing the excessiveamount of the engine torque with respect to the vehicle requirementtorque.
 5. The hybrid vehicle control device according to claim 2,wherein the controller limits a regenerative torque during regenerationof the drive motor, the regeneration of the motor for absorbing anexcessive amount of the engine torque with respect to the vehiclerequirement torque.
 6. The hybrid vehicle control device according toclaim 3, wherein the controller limits a regenerative torque duringregeneration of the drive motor, the regeneration of the drive motorbeing for absorbing the excessive amount of the engine torque withrespect to the vehicle requirement torque.
 7. The hybrid vehicle controldevice according to claim 1, wherein the controller limits a poweringtorque during powering of the drive motor, the powering of the drivemotor being for compensating for the deficient amount of the enginetorque with respect to the vehicle requirement torque.
 8. The hybridvehicle control device according to claim 2, wherein the controllerlimits a powering torque during powering of the drive motor, thepowering of the drive motor being for compensating for the deficientamount of the engine torque with respect to the vehicle requirementtorque.
 9. The hybrid vehicle control device according to claim 3,wherein the controller limits a powering torque during powering of thedrive motor, the powering of the drive motor being for compensating forthe deficient amount of the engine torque with respect to the vehiclerequirement torque by the motor.
 10. The hybrid vehicle control deviceaccording to claim 1, wherein the controller limits the drive motortorque that is required to move the hybrid vehicle backward when areverse range is selected.
 11. The hybrid vehicle control deviceaccording to claim 2, wherein the controller limits the drive motortorque that is required to move the hybrid vehicle backward when areverse range is selected.
 12. The hybrid vehicle control deviceaccording to claim 3, wherein the controller limits the drive motortorque that is required to move the hybrid vehicle backward when areverse range is selected.
 13. The hybrid vehicle control deviceaccording to claim 1, wherein the controller adjusts the engine torqueequivalent to the limited drive motor torque amount.
 14. The hybridvehicle control device according to claim 10, wherein the controllerstops the engine when the reverse range is selected.
 15. The hybridvehicle control device according to claim 11, wherein the controllerstops the engine when the reverse range is selected.
 16. The hybridvehicle control device according to claim 12, wherein the controllerstops the engine when the reverse range is selected.
 17. The hybridvehicle control device according to claim 1, wherein the hybrid vehicleincludes: an engine: the drive motor; a generator; an output shaftconnected to a drive wheel; and a differential gear unit having threegear elements, each gear element being connected to the engine, thegenerator, and the output shaft, and the drive motor being connected tothe output shaft.
 18. A hybrid vehicle control method, comprisingdetecting a torque limit index, which is an index that limits a drivemotor torque of a drive motor that compensates for an excessive or adeficient amount of engine torque with respect to a vehicle requirementtorque vehicle; determining whether the torque limit index has exceededa threshold value; limiting the drive motor torque when the torque limitindex has exceeded the threshold value; and adjusting the engine torquein accordance with the limiting of the drive motor torque.
 19. A programof a hybrid vehicle drive control as apparatus, comprising: a routinethat determines whether a torque limit index has exceeded a thresholdvalue, a routine that limits a drive motor torque when the torque limitindex has exceeded the threshold value; and a routine that adjusts anengine torque in accordance with the limiting of the drive motor torque.20. A hybrid vehicle control device, comprising: a drive motor thatcompensates for an excessive or a deficient amount of engine torque withrespect to a vehicle requirement torque; and a controller that:determines whether a torque limit index has exceeded a threshold value,limits a drive motor torque when the torque limit index has exceeded thethreshold value; and adjusts an engine torque in accordance with thelimiting of the drive motor torque.